Thanks for the comment.
No worries at all, this issue has long been fixed in new (and last) v1.2 demo. In addition, a window and a letterbox mode were added to support these large resolutions / monitors, without losing the original aspect ratio i.e. no stretching.
New v1.2 (demo) build has been already playtested and already working on last bits, expect it in few days with tons of improvements and original content :)